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Seroprevalence to BVDV of alpacas in Southern California. Lisa A. Shimeld, M.S. Crafton Hills College Alpacas del Valle Cereza. Sterling 925. Crafton Hills College Yucaipa, California. Alpacas del Valle Cereza Cherry Valley, California. Suri & Huacaya Alpacas. Some Background.

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seroprevalence to bvdv of alpacas in southern california

Seroprevalence to BVDV of alpacas in Southern California

Lisa A. Shimeld, M.S.

Crafton Hills College

Alpacas del Valle Cereza

Sterling 925

some background
Some Background
  • Alpacas have become an important livestock species in North America since their introduction in 1984
  • They are raised for their soft and luxurious fleeces and there are more than 4,000 alpaca breeders in the United States alone
slide6

It has come to the attention of the alpaca community that BVDV is capable of infecting alpacas, of which there are over 100,000 in North America

  • BVDV infections in alpacas have been reported in the United States and in other parts of the world including Peru and the United Kingdom
  • The potential economic loss to the alpaca community worldwide should not be underestimated
slide7

Prior to 2005 BVDV was virtually unheard of in the mainstream North American alpaca community

We began screening for BVDV on our ranch early in 2006 by PCR and SN testing our breeding males

slide8

Snow Hawke

Much to our dismay, some of those males were seropositive to BVDV

Thankfully all of them were PCR negative

slide9

The rest of the population on our ranch (>100) was PCR and SN tested

No persistently infected (PI) animals were identified but we determined several of our females were seropositive

As we began to educate ourselves on BVDV we realized that a PI cria was likely to have been born on our ranch in April, 2004

slide10

The alpaca we suspected was persistently infected (a black suri male) was tested (3 times)

    • The results of all 3 BVDV PCR tests were positive
  • We believe the exposure that produced the PI suri cria occurred at a ranch in Nevada where his dam bred and lived until the 7th month of her pregnancy
  • At this point the infected female moved to our ranch where she delivered the PI cria
slide11

Mika

  • She remained on our ranch (with her cria ) to rebreed and then moved to a small alpaca facility in Central California
  • We believe the BVDV exposures on our ranch occurred while the dam and infected cria resided with us
introduction
Introduction
  • This project investigates the prevalence of alpacas seropositive to BVDV in Southern California using the serum neutralization (SN) method of testing

Hawke’s Donna Lisa

slide13

It is uncommon to vaccinate against BVDV in the alpaca community for several reasons including a lack of data regarding the effectiveness and safety of BVDV vaccine in this species

SN testing alpacas to detect antibodies to BVDV provides valuable information about exposure to field strains of the virus and will help the alpaca community determine the extent of exposure in the national herd

slide14

Herds with seropositive alpacas can then be further tested to detect the presence of persistently infected (PI) individuals

  • Identification and elimination of PI animals has proven to be the most effective way to control BVDV in cattle herds and should prove to be important in the alpaca population as well
  • Clinical signs of BVDV infection have been reported in Old World (OWC) and New World Camelids (NWC) and are similar to those seen in cattle
purpose of this study
Purpose of this Study
  • The purpose of this study is to use the serum neutralization method of testing to detect antibodies against BVDV in alpacas living or breeding in Southern California, and specifically to:

Morningstar

slide16

Identify alpacas seropositive to BVDV from 24 ranches in Southern California

  • Identify alpacas seropositive to BVDV from ranches outside of Southern California breeding in Southern California
  • Determine the prevalence of BVDV in alpacas in Southern California
transmission of bvdv
Transmission of BVDV
  • BVDV is believed to have originally entered the North American alpaca population through contact with infected cattle but exposure to BVDV infected wildlife has likely occurred as well
slide18

As in cattle, the virus is transmitted in two ways: vertically (dam to cria) and horizontally (from one to another member of the same population) although a persistent infection can only occurthrough vertical transmission

Persistently infected (PI) animals are more likely to be responsible for the horizontal transmission of BVDV than acutely infected animals

slide19

Kennedy found PI cattle shed thousands more viral particles for the duration of their lives than animals with transient infections (Kennedy, 2005)

  • Acutely infected cattle shed the virus for a period of three to four weeks and are a potential source of infection for other animals during that time but may remain seropositive for years after the infection has cleared from their system
slide20

In bovines, vertical transmission of BVDV occurs when a pregnant female is infected (during her pregnancy)

    • The virus crosses the placental barrier and infects her fetus
  • The outcome depends upon the stage of pregnancy that the infection occurred:
    • Absorption, abortion, a stillborn fetus, or a PI calf, have all been reported, the later possibility being most likely when the dam is infected within 125 days of conception as shown in Table 1
slide22

Vertical transmission of BVDV also occurs if a PI cow becomes pregnant and carries her fetus to term – a PI calf is always the result

    • This is a less common mode of transmission as PI cows are difficult to impregnate
  • As alpacas gestate 60 days longer than cows (342 days vs. 282 days), the window of exposure for the production of a PI cria in the former case is probably somewhat different than that of a PI calf
slide23

Horizontal transmission of BVDV occurs via respiratory secretions, saliva, feces, urine or semen. Respiratory secretions and saliva contain the highest infectious dose (Confer et al., 2005)

Infection most often occurs through the oral and nasal routes

slide24

AVC Dr. Feelgood

To the best of our knowledge, no research has been published to suggest transmission of BVDV in alpacas differs from that of cattle

materials and methods
Materials and Methods

Animals in the study and sampling procedures:

  • Two hundred ninety six alpacas living in Southern California, or present in Southern California to breed, were included in this study, the majority being located in either Riverside (179) or Los Angeles (86) county
slide27

Table 2. Location of facilities in this study by county and state and number of alpacas tested in each county

slide28

Double Trouble

The subjects included 223 females and 73 males ranging in age from one hour old to 17 years of age

slide29

Herd size ranged from four to 280 alpacas

Percentage of the herds tested ranged from 21% of the herd of 280 to 100% of other herds including a herd of 130

All alpacas appeared clinically normal at the time of sampling

slide30

Blood (2 – 3 ml) was drawn from the jugular vein of the subjects and stored in red top anticoagulant-free vacutainer tubes

  • The samples were shipped to the California Animal Health & Food Safety Laboratory System in Davis, California for serum neutralization testing for BVDV
slide31

Lisa & Morningstar

There was no known contact between cattle and any of the alpacas in this study

The use of BVDV vaccines was not reported in any of the alpacas in this study

slide32

Serological testing

Serum virus neutralization (SN) was performed to measure the titer of circulating antibody to BVDV type 1 and to BVDV type 2, using NADL and c125 BVDV as reference strains, respectively

slide33

Samples were tested in duplicate, using serial two-fold dilutions of heat-inactivated serum, a 100-500 TCID50, bovine fetal testicle primary cell culture, and 96-hours incubation at 37° C in 5% CO2

Results were reported as the endpoint serum dilution that demonstrated no observed cytopathic effect in the assay

results
Results
  • Fifty five of the 296 alpacas tested were seropositive to one or both BVDV genotypes and of these 49 had BVDV type 1 titers that were higher than their BVDV type 2 titers
  • Nine of the alpacas seropositive to BVDV type 1 were seronegative to BVDV type 2
  • BVDV type 1 titers ranged from 1:8 to >1:8192 and BVDV type 2 titers were between 1:8 and 1:2048
slide36

Fourteen of the alpacas tested were females present in Southern California to breed, and two of these were accompanied by their crias who were also tested

Of these sixteen alpacas, two were found to be seropositive to BVDV types 1 and 2 with type 1 titers of >1:512 and 1:512 and type 2 titers of 1:128 and 1:16 respectively

slide37

Table 4. Number of male and female alpacas seropositive to BVDV type 1 and BVDV type 2 by county and state.

slide38

Three PI alpaca crias were identified and were born on different ranches participating in this study

Some of the highest titers recorded in this study were from those ranches

None of the seropositive alpacas identified in this study showed any clinical signs of infection

discussion and conclusions
Discussion and Conclusions
  • This study was designed to determine the prevalence of alpacas seropositive to BVDV in Southern California
  • The results of the current study suggest that alpacas seroconvert when exposed to BVDV but clinical disease is unusual
slide40

18.6% of the alpacas SN tested in this study were seropositive for one or both BVDV genotypes

None of the alpacas in this study were reported having any contact with cattle. Alpacas vaccinated against BVDV would likely have titers for an as of yet undetermined time but the use of BVDV vaccines was not reported in any of the alpacas in this study

slide41

If contact with infected cattle and titers due to vaccination are not responsible for these seropositive alpacas then they were exposed to acutely or persistently infected alpacas or other species sometime during their life

The three PI alpaca crias identified in this study emphasize this as their dams had to be exposed to BVDV during the early stages of gestation to produce PI crias

slide42

Sehiya

In conclusion, the results show that seropositive alpacas and PI alpacas are present in the Southern California alpaca population and that alpacas can have BVDV titers even though they have never been exposed to infected cattle or vaccinated for BVDV

slide43

Mewy & Donna Lola

While the current study was limited to Southern California the results obtained support the need for further sampling of the North American alpaca population to determine the prevalence of BVDV exposure and to identify and eliminate PI alpacas from the national herd

slide44

MacDuff

Further investigations regarding the prevalence of BVDV in the South Western United States are in progress